The formation of metastases of malignant tumors, initiated from a primary tumor at more or less remote locations of the body, is one of the most serious effects of cancer and one for which a satisfactory treatment protocol is currently unavailable. Cancer tumor metastasis is responsible for most therapeutic failures when the disease is treated, as patients succumb to the multiple tumor growth.
The extent to which metastasis occurs varies with the individual type of tumor. Melanoma, breast cancer, lung cancer, colon cancer and prostate cancer are among the types of cancer that are particularly prone to metastasize. When metastasis takes place, the secondary tumors can form at a variety of sites in the body, with lungs, liver, brain and bone being the more common sites.
The currently available methods of cancer therapy such as surgical therapy, radiotherapy, chemotherapy and other immunobiological methods have either been unsuccessful in preventing metastasis or these methods give rise to serious and undesirable side effects.
In many clinically diagnosed solid tumors (in which the tumor is a localized growth) surgical removal is considered the prime means of treatment. However, many times after surgery and after some delay period, the original tumor is observed to have metastasized so that secondary sites of cancer invasion have spread throughout the body and the patient subsequently dies of the secondary cancer growth. Reports indicate that in individuals with resectable tumors, primary tumor growth or local recurrence is not often the cause of death. Instead, at present, nearly 40% of cancer victims with operable tumors ultimately succumb to metastatic disease following surgery.
Metastasis is a constant occurrence in some tumors. However, many times metastasis is triggered by the surgical operation itself. During the course of surgery malignant cells may become dislodged from the tumor mass and enter the circulatory system thus increasing the chance of metastasis.
Although chemotherapy is widely used in the treatment of cancer, it is a systemic treatment based usually on the prevention of cell proliferation. Accordingly, chemotherapy is a non-specific treatment modality affecting all proliferating cells, including normal cells, leading to undesirable and often serious side effects such as immunosuppression, pancytopenia (growth inhibition of bone marrow cells with anemia, thrombocytopenia and leukopenia), diarrhea, nausea and alopecia (hair loss).
Generally, the existing systemic treatments have, quite often, proven to have little effect on micrometastases already residing in remote organs (lung, liver, bone marrow or brain), and they are not very effective in preventing the dissemination of the tumor to other tissues.
Therefore, the need exists for methods of inhibiting tumor metastasis. In particular, methods which inhibit metastasis without causing serious side effects are much desired.